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Table 5.2 Results of Optimization of Cooling Channel Distance in Figure 5.50
Input
Mold pressure
Maximum deflection
Modulus of elasticity
Modulus of shear
Allowable tensile stress
Allowable shear stress
Channel dimension
P - 4.9 N/mm 2
/max = 2.5 Um
jT = 70588 N/mm 2
G = 27147 N/mm 2
=421.56 N/mm 2
The equations given provide approximate values for circular channels as well. The distance
from wall to wall of the channel should be approximately the channel length / or channel
diameter, taking the strength of the mold material into account.
53.6 Melting in Injection Molding Screws
The plastication of solids in the reciprocating screw of an injection molding machine is
a batch process and consists of two phases. During the stationary phase of the screw
melting takes place mainly by heat conduction from the barrel. The melting during screw
rotation time of the molding cycle is similar to that in an extrusion screw but instationary.
With long periods of screw rotation, it approaches the steady state condition of extrusion
melting.
5.3.6.1 Melting by Heat Conduction
ah
D max ,
Tmax =294.1 N/mm
/ = 10 mm
Output
Channel distance
Deflection
Tensile stress
Shear stress
d =2.492 mm
/ = 2.487 um
G =39.44 N/mm 2
T = 14.75 N/mm 2
According to DONOVAN [28], the equation describing conduction melting can be written as
where
T = temperature 0 C
A = thermal conductivity W/(m • K)
K = Parameter defined by [28] m/s 0 * 5
a = thermal diffusivity m 2 /s
I = latent heat of fusion kj/kg
p = density g/cm 3
Indices:
r: middle of solid bed
s: solid
m: melt
b: barrel
(5.96)